1. Field of the Invention
This invention relates to a photoconductive member having sensitivity to electromagnetic waves such as light (herein used in a broad sense, including untraviolet rays, visible light, infrared rays, X-rays and gamma-rays) and a device for producing the same.
2. Description of the Prior Art
Photoconductive materials, which constitute image forming members for electrophotography in solid state image pick-up devices or in the field of image formation, or photoconductive layers in manuscript reading devices, are required to have a high sensitivity, a high SN ratio (Photocurrent (I.sub.p)/Dark current (I.sub.d)), spectral characteristics matching to those of electromagnetic waves to be irradiated, a rapid response to light, a desired dark resistance value as well as no harmful effects to human bodies during usage. Further, in a solid state image pick-up device, it is also required that the residual image should easily be treated within a predetermined time. In particular, in case of an image forming member for electrophotography to be assembled in an electrophotographic device to be used in an office as office apparatus, the aforesaid safety characteristic is very important.
From the standpoint as mentioned above, amorphous silicon in which dangling bonds are modified with mono-valent elements such as hydrogen or halogen atoms (hereinafter referred to as a-Si(H, X)) has recently attracted attention as a photoconductive material. For example, German Laid-Open Patent Publication Nos. 2746967 and 2855718 disclose its applications for use in image forming members for electrophotography, and German Laid-Open Patent Publication No. 2933411 its application for use in a photoconverting reading device. It is expected to be useful in an image forming member for electrophotography for excellent photoconductivity, friction resistance, heat resistance and relative ease in forming into a large area.
Generally speaking, when an image forming member for electrophotography is mounted on a copying machine and image formation is effected in a highly humid environment, a defect known as the image flow, accompanied with an unfocused image or a disappearance of image, will frequently occur. This is because products from corona discharge or paper powder attached on the surface of an image forming member absorb water to lower the surface resistance of the image forming member, whereby the image forming member can no longer retain the electrostatic latent image. It has been difficult to remove such attached materials selectively from the surface of an image forming member, and it is common to remove the attached materials by incorporating a substance having the effect of removing the attached materials through attrition in a developer. However, upon the effective removal of the attached materials, the surface layer will also be abraded little by little. Abrasion of the surface layer of the image forming member has deleterious effects on the photosensitive characteristics and image quality, despite preventing image defects such as image flow. Thus, this method is not necessarily a good technique for overcoming this problem.
In view of the above points, the present invention is based on a discovery, obtained as a result of extensive studies made comprehensively from the standpoints of applicability and utility of a-Si as a light-receiving member for image forming members for electrophotography, solid state image pick-up devices, reading devices, etc., that the surface of a photoconductive member, which is liable to cause image flow, has a very low contact angle with water. On the basis of this knowledge, studies have been made to enhance the contact angle of the surface of a photoconductive member with water. Consequently, it has now been found that the above problem can be overcome by making the contact angle with water of the surface of a light receiving layer containing an amorphous material comprising silicon atoms as the matrix, higher than a certain value. Products from corona discharge or paper powder may have some influence on the contact angle of the surface of a photoconductive member. The above effect may be postulated to be due to the fact that such deleterious effects due to the corona product or paper powder may be alleviated when the surface has originally a contact angle of a certain value or higher.